Comparison of static and dynamic response of timber shear walls

Static and dynamic tests were conducted on wood frame shear walls to (1) determine the wall resistance to lateral loading; (2) examine the wall performance under fully reversed cycles of dynamic loading; and (3) compare the static and dynamic performance as measured using the same test facility. Tests were conducted on standard 2.44 by 2.44 m (8 by 8 ft) walls, constructed of plywood or oriented strand board sheathing. Four specimens were tested statically using the traditional ASTM E-564 test procedure: three half-cycles, loading monotonically to failure. Eight specimens were tested dynamically, using a proposed test standard that was recently developed by the Structural Engineers Association of Southern California. A comparison of the static and dynamic test results demonstrates several key differences. The ultimate loads measured in the dynamic tests are slightly less than those measured in the static tests; however, the ductility of the wall, when measured dynamically, is between 34 and 42% less than the corresponding static ductility. Furthermore, damage in the static tests is characterized by the pulling away of the sheathing from the frame, extraction of the sheathing nails, and splitting of the bottom plate. Damage in the dynamic tests is generally confined to pullout and fatiguing of the sheathing nails, which eventually break off. The dynamic tests show a reduction in load and stiffness and pinched hysteresis with continued cycling at a given displacement. The results of this study suggest that the actual load factors for a shear wall subjected to an earthquake will be significantly lower than the intended design.